Attempts have been made to configure an electronic percussion instrument in a manner to simulate an acoustic percussion instrument. For example, Japanese Laid-open Patent Application 2004-198657 describes an electronic percussion instrument 1 that includes a head 5, a rim 6, a shell section 2, a sensor frame 4, and a rim shot sensor 31. The head 5 has a striking surface. The rim 6 surrounds the head 5. The head 5 and the rim 6 are arranged in a manner to cover the shell section 2. The sensor frame 4 is formed in a container-like shape, and supported between the shell section 2 and the rim 6. The rim shot sensor 31 is directly attached to the sensor frame 4. Accordingly, when the rim 6 is struck, causing the rim 6 to vibrate, the vibration is transmitted from the rim 6 to the sensor frame 4 and is detected by the rim shot sensor 31. A controlled tone is generated based on the detected signal.
However, a conventional electronic percussion instrument 1 as described above can be influenced by external sound such as sound emanated from loudspeakers, because the surface area of the sensor frame 4 is relatively large. Therefore, even when the rim 6 is not struck, external sound propagated through the air can be transmitted to the sensor frame 4. As a result, the sensor frame 4 can vibrate due to resonance, which can cause erroneous detection of a strike on the rim 6 by the rim shot sensor 31.